1. Field of the Invention
The present invention relates to a liquid crystal display module. More particularly, the present invention relates to a liquid crystal display module capable of improving the brightness and light efficiency of a direct-below-type back light unit.
2. Discussion of the Related Art
Uses for liquid crystal display modules (hereinafter, LCM) have gradually increased due to the LCM's light weight, its thinness, and low power consumption. For example, the LCM may be used in an office automation device, audio/video devices and the like. The LCM adjusts a transmittance quantity of a light beam in accordance with an image signal applied to a matrix of a plurality of control switches to thereby display desired pictures on a screen.
Because the LCM is not a spontaneous light-emitting display device, the LCM needs a back light unit as a light source. There are two types of back light units for the LCM, i.e., a direct-below-type and a light guide plate-type.
The direct-below-type LCM has a plurality of lamps arranged in series below the liquid crystal panel. A diffusion plate is installed between the lamps and the liquid crystal panel and maintains a gap between the lamps and the liquid crystal panel. The light guide plate-type LCM has a lamp installed on the outside of the light guide plate, and irradiates light from the lamp to the liquid crystal display panel using a transparent light guide plate.
In FIG. 1, a related art liquid crystal display module includes: a plurality of lamps 12, placed in parallel with each other, for generating light; a reflection plate (or a lamp housing) 10 for accommodating the lamps 12; a diffusion plate 16 for covering an aperture part of the lamp housing 10; an optical film 18 sequentially stacked on the diffusion plate 16; and a liquid crystal display panel 6 arranged on the optical film 18.
The liquid crystal display panel 6 includes an upper substrate 3 and a lower substrate 5. Liquid crystal materials are injected between the upper substrate 3 and the lower substrate 5. The liquid crystal display panel 6 is provided with a spacer (not shown) for maintaining a gap between the upper substrate 3 and the lower substrate 5. The upper substrate 3 of the liquid crystal display panel 6 is provided with a color filter, a common electrode and a black matrix (which are not shown). Signal lines such as a data line and a gate line (not shown) are formed on the lower substrate 5 of the liquid crystal display panel 6. A thin film transistor (TFT) is formed at a crossing of the data line and the gate line. The TFT switches a data signal to be transmitted from the data line to the liquid crystal cell in response to a scanning signal (i.e., a gate pulse) from the gate line. A pixel electrode is formed at a pixel area defined between the data line and the gate line. A pad area is formed in one side of the lower substrate 5 and is connected to each of the data line and the gate line. A tape carrier package (not shown) having a driver integrated circuit mounted thereon to apply a driving signal to the TFT is attached on the pad area. The tape carrier package applies a data signal and the scanning signal from the driver integrated circuit to each of the data line and the gate line.
An upper polarizing sheet is attached on the upper substrate 3 of the liquid crystal display panel 6 and a lower polarizing sheet is attached on of the rear side of the lower substrate 5 of the liquid crystal display panel 6. The upper and lower polarizing sheets function to enlarge a viewing angle of a picture displayed by a liquid crystal cell matrix.
Each of the lamps 12 includes a glass tube, inert gases filled within the glass tube, and a cathode and an anode installed at opposite ends of the glass tube. The inner wall of the glass tube is coated with phosphors.
When an alternating-current voltage from an inverter (not shown) is applied to the anode and the cathode of each lamp 12, electrons are emitted from the cathode. The emitted electrons collide with the inert gases contained in the glass tube, and the number of electrons exponentially grows. The increased electrons generate electric currents in the glass tube, and excite the inert gases (For example, Ar, Ne) to generate energy. The energy excites mercury which emits ultraviolet rays. The ultraviolet rays collide with the phosphors coated on the inner wall of the glass tube to generate visible light.
The reflection plate 10, made of an aluminum material, prevents leakage of the visible light emitted from each of the lamps 12, and reflects the visible light that reaches the sides and rear of the reflection plaTe to the front side thereof, i.e., to the diffusion plate 16, to increase the efficiency of light emitted from the lamps 12.
The diffusion plate 16 causes the light emitted from the lamps 12 to go toward the liquid crystal panel 6 with a wide range of incident angle. The diffusion plate 16 includes a transparent resin film whose both surfaces are coated with light-diffusion materials.
The optical film 18 increases the efficiency of light outgoing from the diffusion plate 16 to irradiate the light to the liquid crystal display panel 6.
As mentioned above, the related art LCM uses a plurality of lamps 12 to generate a uniform light, and then irradiates the light to the liquid crystal panel 6 to display pictures thereon. However, the related art LCM also uses a plurality of the lamps 12 to improve efficiency and brightness of the light irradiated to the liquid crystal display panel 6. Accordingly, in the related art LCM, when the number of the lamps 12 is reduced, a problem occurs in which brightness and efficiency are deteriorated.